The most recent addition to the synthetic insect
repellents on the market in the United States is
IR3535,
22
which is classified by the Environmental
Protection Agency as a biopesticide because of its
structural similarity to the amino acid alanine. This
repellent has been used in Europe for more than 20
years and was approved for use in the United States
in 1999. In our tests, this repellent fared poorly, yielding
a mean complete-protection time that was one
quarter that of the lowest-concentration DEET product
we tested (22.9 vs. 88.4 minutes).